1. Field of the Invention
The present invention relates to spring mechanisms used with lock mechanisms to return a handle to an original position after the handle has been rotated to open a door. The invention is particularly directed to spring mechanisms to be used with lever handles and lock mechanisms having lock function controls extending outward from a latchbolt mechanism to return the lever handle to a horizontal position.
2. Description of Related Art
Lock mechanisms are driven by inner and outer handles mounted on corresponding spindles that extend from the handles on opposite sides of the door to a lock mechanism located within a bored opening in the door. A latchbolt portion of the lock mechanism is located within a smaller bored opening that extends inward from the edge of the door and perpendicularly intersects the larger bored opening, which extends between the opposite faces of the door.
After one of the handles is turned to open the door, it must be returned to its initial position and this return function is typically accomplished with one or more springs. The return springs may be integrated into the lock or they may be located in a separate housing mounted inside the bored opening and/or on the surface of the door at the base of the handle.
When round doorknobs are installed, relatively little force is required to return the doorknob to its initial position, however, it has become more common to install lever handles. Although lever handles are easier to operate, they require the return spring assembly to produce significantly more torque to lift the offset portion of the lever handle against the force of gravity and return it to the initial horizontal orientation. As a consequence, it has become necessary to use larger and more powerful return springs than were previously necessary for round doorknobs.
Larger springs generally require more space than can easily be found inside the lock mechanism, so separate return spring mechanisms are widely used—one located on each side of the door. When the return spring mechanism is mounted on the outer surface of the door, however, it produces a relatively thick and bulky appearance, which is unsightly. A thinner appearance is preferred, and this requires that the springs be located at least partially inside the bored opening of the door. However, positioning the return spring assembly inside the bored opening in the door limits the space available for the lock mechanism, which must also be located within the bored opening.
Conventional designs that position the return spring assembly inside the bored opening use one or more springs that extend around substantially the entire inner perimeter of the bored opening on each side of the door. This provides the maximum space for the spring and allows it to maximize the torque produced. The spring force on each side of the door may come from one large compression spring, or from a pair of compression springs arranged end to end, or from a coiled torsion spring. In each case, however, the spring extends around a substantial portion of the inside perimeter of the bored opening.
This use of the inner perimeter of the bored opening is acceptable for many door lock mechanisms where the locking mechanism is in a central lock core. In these designs the interaction between the user and the locking mechanism comes from a button or key on the handle that connects to the locking mechanism through linkages or mechanisms that are located close to or directly on the axis of the bored opening in the door. By placing the lock control linkages close to this axis, the linkages are positioned well inside the perimeter space required for the locking springs and there is no interference between the springs and the lock mechanism linkages.
However, in other lock mechanism designs, of the type for which this invention is particularly suitable, the locking mechanism is more closely integrated with the latchbolt portion. In these designs, the lock control linkages extend directly outward from the latchbolt mechanism at the front of the lock mechanism bored opening and the lock linkages are far from the axis of rotation of the handles. As a result, the lock control linkages in such designs will interfere with the springs in a conventional spring return mechanism where the springs occupy the entire inner circumference of the bored opening.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a return spring assembly that is compatible with lock mechanisms having a control linkage extending outward from the latchbolt mechanism.
It is another object of the present invention to provide a return spring assembly that does not extend into the space at the front of a bored opening in a door and has the spring mechanism located at least partially inside the bored opening to provide a reduced visual thickness as compared to return spring assemblies that are mounted outside the bored opening on the surface of the door.
It is another object of the present invention to provide a return spring assembly that provides additional support to the latchbolt mechanism of a lock mechanism.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.